Technical Field
The present invention relates to a system and methods for determining the haze of a thin film deposited on a substrate. Particularly, the system and methods measure the haze of a thin film, such as a transparent conductive film deposited on a substrate, by either the reflectance of light by the external surface or the scattering of light by the internal grain surfaces of the thin film.
Conventionally, the word "haze" is defined as the ratio of the diffuse (i.e. scattered) component of transmitted light to the total amount of light transmitted by a thin film for the wavelengths of light to which the photodetector is sensitive. However, as used herein, the word "haze" means the macroscopically observable ability of a thin film to scatter, reflect or transmit light in reference to an arbitrary relative haze scale. The haze scale is established by setting 50-90 samples of ZnO of varying "haziness" against a black background, then based on their relative haziness to the eye of an observer, they are arbitrarily assigned a number between 1 and 10 with a resolution of 0.5. Coarse assignments of the sample are made first; then detailed decisions are made by side-by-side comparisons of the samples.
As used herein, the word "fringer" means an optical measurement system for measuring the thickness and haze of thin films based on the optical interference ("fringes") observed in the spectrum of light reflected or scattered from the thin film surface.
As used herein, the word "transparent conductor" means a thin film having a sheet resistance value useful for fabricating practical photoconductor devices and also exhibiting a peak optical transmission of greater than about 75% in the wavelength range to which the photoconductor is sensitive.